Semiconductor wafer with non-rectangular shaped dice

ABSTRACT

A semiconductor wafer having a plurality of dice formed on the wafer. The plurality of dice having non-rectangular shapes with at least one notched corner. A plurality of saw streets are defined between the plurality of dice. At an intersection of two of the plurality of saw streets, a distance is defined between corners of two adjacent dice that is greater than a minimum distance between the two adjacent dice.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/453,921, titled A PROCESS OF BETTER DESIGNING RETICLE FIELDS, filedMar. 13, 2003, the entire content of which is incorporated herein byreference.

BACKGROUND

1. Field of the Invention

The present application relates generally to integrated circuit designand fabrication on a semiconductor wafer and, more particularly, tofabricating non-rectangular dice among a plurality of saw streets on asemiconductor wafer.

2. Related Art

In semiconductor wafer processing, integrated circuits (ICs) are formedon a semiconductor wafer. In general, layers of various materials, whichare either semiconducting, conducting or insulating, are utilized toform the ICs. These materials are doped, deposited and etched usingvarious well-known processes to form the ICs. Each semiconductor waferis processed to form a large number of individual regions containing ICsknown as dice. Test circuits, test pads and alignment markings may alsobe formed on the wafer in regions between the dice referred to as sawstreets.

Following the integrated circuit formation process and before dice areseparated, a full wafer may be tested. While multiple dice are attachedtogether on a single wafer, semiconductor manufactures often performwafer level testing of the dice. The test circuits and test pads formedin the saw streets between the dice are used to assist in performing thewafer level testing of the dice. Wafer level testing identifies bad dicebefore further effort is expended in testing and packaging. Therefore,wafer level testing allows a manufacturer to identify and discardunsatisfactory dice.

Following testing, the wafer is diced to separate the individual dicefrom one another for packaging or for use in an unpackaged form withinlarger circuits. Two techniques for wafer dicing include scribing andsawing. With scribing, a diamond tipped scribe is moved across the wafersurface along pre-formed scribe lines. These scribe lines extend alongthe saw street between the dice. Any test circuits, test pads andalignment marks positioned in a saw street are sacrificed. Thus, thesestructures can be referred to as sacrificial structures.

As mask layout tolerances decrease and cutting techniques improve, theremay also be a corresponding decrease in distance between individual diceon a semiconductor wafer. Therefore, the width of the saw streetsbetween individual dice may also narrow. The resulting saw streets mayleave little room for sacrificial structures.

SUMMARY

In one exemplary embodiment, a semiconductor wafer has a plurality ofdice formed on the wafer. The plurality of dice having non-rectangularshapes with at least one notched corner. A plurality of saw streets aredefined between the plurality of dice. At an intersection of two of theplurality of saw streets, a distance is defined between corners of twoadjacent dice that is greater than a minimum distance between the twoadjacent dice.

DESCRIPTION OF DRAWING FIGURES

The present application can be best understood by reference to thefollowing description taken in conjunction with the accompanying drawingfigures, in which like parts may be referred to by like numerals:

FIG. 1 shows a side view of an exemplary reticle positioned over asemiconductor wafer.

FIG. 2 shows a plan view of the reticle depicted in FIG. 1.

FIG. 3 shows a plan view of structures formed on a wafer using thereticle depicted in FIGS. 1 and 2.

FIGS. 4-7 show additional plan views of structures formed on a wafer.

DETAILED DESCRIPTION

The following description sets forth numerous specific configurations,parameters, and the like. It should be recognized, however, that suchdescription is not intended as a limitation on the scope of the presentinvention, but is instead provided as a description of exemplaryembodiments.

Circuit designers provide circuit pattern data, which describes aparticular IC design, to a reticle production system, or reticle writer.The circuit pattern data is typically in the form of a representationallayout of the physical layers of the fabricated IC device. Therepresentational layout typically includes a representational layer foreach physical layer of the IC device (e.g., gate oxide, polysilicon,metallization, etc.). The representational layout may also include oneor more representational layers defining structures positioned oversacrificial areas (e.g., over saw streets). These sacrificial structuresmay include alignment markings, identification markings, measurementmarkings, test pads, test circuitry, and the like.

The reticle writer uses the circuit pattern data to write (e.g., usingan electron beam writer or laser scanner to expose a reticle pattern) aplurality of reticles that will later be used to fabricate theparticular IC design and sacrificial structures.

A reticle or photomask is an optical element containing at leasttransparent and opaque regions, and sometimes semi-transparent and phaseshifting regions, as well, which together define the pattern of coplanarfeatures in an electronic device such as an IC and sacrificialstructures. Reticles are used during a photolithographic process todefine specified regions of a semiconductor wafer for etching, ionimplantation, or other fabrication process. For many modern IC designs,an optical reticle's features are between about one and about five timeslarger than the corresponding features on the wafer. For other exposuresystems (e.g., x-ray, e-beam, and extreme ultraviolet) a similar rangeof reduction ratios also apply.

FIG. 1 depicts an exemplary embodiment of a reticle 6 positioned over awafer 10 during IC fabrication in a chamber 2. The chamber 2 exposes thereticle 6 with laser light 4 or the like. Light that passes through thereticle 6 is directed with a lens 8 to the wafer 10. A photolithographicprocess may use one or more reticles to simultaneously create aplurality of integrated circuits and sacrificial structures on thewafer. Thus, a wafer may contain several to thousands of separateintegrated circuits.

A single wafer may be divided along boundaries between the individualdevices by scoring or cutting along axes referred to as scribe lines inthe saw streets. Some or all of the sacrificial structures may bedestroyed during dicing. Separation or dicing may be performed bysawing, laser cutting, and the like.

FIG. 2 depicts reticle 6 defining a plurality of die images 101-109,which can be used to form dice on a wafer through a photolithographicprocess. In the present exemplary embodiment, die images 101-109 havenon-rectangular shapes with at least one notched corner. A plurality ofsaw street regions 61, 62 are defined between die images 101-109. At anintersection of two saw street regions 61, 62, a distance D1 is definedbetween the corners of two adjacent die images that is greater than aminimum distance D2 between the two adjacent die images.

In the present exemplary embodiment, die images 101-109 also have atleast one side not parallel to saw street regions 61, 62. Note thatbecause die images 101-109 have non-rectangular shapes, saw streetregions 61, 62 are non-rectilinear. In FIG. 2, saw street regions 61, 62are depicted as being orthogonal to at least one side of die images101-109. It should be recognized, however, that saw street regions 61,62 can be non-orthogonal to any sides of die images 101-109. In FIG. 2,die images 101-109 are depicted as having an octagonal shape. It shouldbe recognized, however, that die images 101-109 can have various shapes,such as hexagonal shapes. Additionally, for simplicity and convenience,the figure shows structures and features having similar horizontal orvertical dimensions in a plane parallel to a wafer. It should berecognized, however, that the horizontal and vertical dimensions candiffer.

As depicted in FIG. 2, reticle 6 also includes sacrificial structureimages 200, which can be used to form sacrificial structures on a waferthrough a photolithographic process. In the present exemplaryembodiment, sacrificial structure images 200 are disposed at theintersection of two saw street regions 61, 62, where distance D1 definedbetween the corners of two adjacent die images is greater than minimumdistance D2 between two adjacent die images. Thus, sacrificial structureimages 200 can have a dimension, such as a width, greater than minimumdistance D2, and the width of saw street regions 61, 62 is not limitedto and can be less than the at least one dimension of sacrificialstructure images 200. In FIG. 2, sacrificial structure images 200 aredepicted as having at least one side orthogonal to saw street regions61, 62. It should be recognized, however, that sacrificial structureimages 200 can have at least one side non-orthogonal to saw streetregions 61, 62.

FIG. 3 depicts structures formed on a wafer using reticle 6 (FIG. 2).For example, dice 111-114 are formed on the wafer from die images 101,102, 104, and 105 (FIG. 2) on reticle 6 (FIG. 2). In the presentexemplary embodiment, because dice 111-114 are formed using reticle 6(FIG. 2), they are formed with non-rectangular shapes with at least onenotched corner. A plurality of saw streets 71, 72 are defined betweendice 111-114. At an intersection of two saw streets 71, 72, a distanceD3 is defined between the corners of two adjacent dice that is greaterthan a minimum distance D4 between the two adjacent dice.

In the present exemplary embodiment, dice 111-114 also have at least oneside not parallel to saw streets 71, 72. Note that because dice 111-114have non-rectangular shapes, saw streets 71, 72 are non-rectilinear. InFIG. 3, saw streets 71, 72 are depicted as being orthogonal to at leastone side of dice 111-114. It should be recognized, however, that sawstreets 71, 72 can be non-orthogonal to any sides of dice 111-114.

Additionally, sacrificial structures 210 are formed on the wafer fromsacrificial structure images 200 (FIG. 2) on reticle 6 (FIG. 2). In thepresent exemplary embodiment, because sacrificial structures 210 areformed using reticle 6 (FIG. 2), they are disposed at the intersectionof two saw streets 71, 72, where distance D3 defined between the cornersof two adjacent dice is greater than minimum distance D4 between twoadjacent dice. Thus, sacrificial structures 210 can have at least onedimension, such as a width, greater than minimum distance D4, and thewidth of saw streets 71, 72 is not limited to and can be less than theat least one dimension of sacrificial structures 210. In FIG. 3,sacrificial structures 210 are depicted as having at least one sideorthogonal to saw streets 71, 72. It should be recognized, however, thatsacrificial structures 210 can have at least one side non-orthogonal tosaw streets 71, 72.

Although dice 111-114 are depicted as having an octagonal shape, itshould be recognized that dice 111-114 can have various non-rectangularshapes, such as hexagonal shapes. For example, FIG. 4 depicts anexemplary embodiment of dice 121-124 with square-notched corners. Asdepicted in FIG. 4, at an intersection of saw streets 71, 72, a distanceD5 defined between the square-notched corners of two adjacent dice isgreater than minimum distance D4.

FIG. 5 depicts another exemplary embodiment of dice 131-134 withcurve-notched corners. As depicted in FIG. 5, at an intersection of sawstreets 71, 72, a distance D6 defined between the curve-notched cornersof two adjacent dice is greater than minimum distance D4.

FIG. 5 also depicts sacrificial structures 210 having a square shape andsacrificial structures 211 having a circular shape. It should berecognized that sacrificial structures 210, 211 can have various shapes.

FIG. 6 depicts still another exemplary embodiment of dice 141-144 withnon-rectangular shapes that are not identical to each other in shape.FIG. 6 also depicts sacrificial structures 212 having a diamond shape.

FIG. 7 depicts yet another exemplary embodiment of dice 151-162 withnon-rectangular shapes and an edge that can be used to orient dice151-162. For example, after dicing the wafer, the shape of a die can beused to orient the die before packaging the die. Additionally, in thepresent exemplary embodiment, alternating rows of dice have similarorientations. After dicing, the alternating rows of dice can be orientedbased on any remaining sacrificial structures 210.

Although exemplary embodiments have been described, variousmodifications can be made without departing from the spirit and/or scopeof the present invention. Therefore, the present invention should not beconstrued as being limited to the specific forms shown in the drawingsand described above.

1. A semiconductor wafer comprising: a plurality of dice formed on thewafer, the plurality of dice having non-rectangular shapes with at leastone notched corner; and a plurality of saw streets defined between theplurality of dice, wherein at an intersection of two of the plurality ofsaw streets, a distance is defined between corners of two adjacent dicethat is greater than a minimum distance between the two adjacent dice.2. The semiconductor wafer of claim 1, wherein the plurality of dicehave at least one side not parallel and non-orthogonal to the sawstreets.
 3. The semiconductor wafer of claim 1, wherein the plurality ofdice have octagonal shapes.
 4. The semiconductor wafer of claim 1,wherein the plurality of dice have hexagonal shapes.
 5. Thesemiconductor wafer of claim 1, wherein the at least one notched corneris square or curved.
 6. The semiconductor wafer of claim 1, wherein thesaw streets are non-rectilinear.
 7. The semiconductor wafer of claim 1,wherein the saw streets are orthogonal to at least one side of theplurality of dice.
 8. The semiconductor wafer of claim 1, wherein thesaw streets are non-orthogonal to any sides of the plurality of dice. 9.The semiconductor wafer of claim 1, further comprising: a sacrificialstructure formed at the intersection of two of the plurality of sawstreets.
 10. The semiconductor wafer of claim 9, wherein the sacrificialstructure has at least one dimension greater than the minimum distancebetween the two adjacent dice.
 11. The semiconductor wafer of claim 10,wherein a width of the plurality of saw streets is less than the atleast one dimension of the sacrificial structure.
 12. The semiconductorwafer of claim 9, wherein at least one side of the sacrificial structureis orthogonal to the plurality of saw streets.
 13. The semiconductorwafer of claim 9, wherein at least one side of the sacrificial structureis non-orthogonal to the plurality of saw streets.
 14. A reticle to formthe plurality of dice and plurality of saw streets in accordance withclaim 1 using a photolithographic process.
 15. A semiconductor wafercomprising: a plurality of dice formed on the wafer, the plurality ofdice having non-rectangular shapes; a plurality of saw streets definedbetween the plurality of dice; and a sacrificial structure formed at anintersection of two of the plurality of saw streets, wherein at theintersection a distance is defined between two adjacent dice that isgreater than a minimum distance between the two adjacent dice.
 16. Thesemiconductor wafer of claim 15, wherein the plurality of dice have atleast one side not parallel to the saw streets.
 17. The semiconductorwafer of claim 15, wherein the plurality of dice have octagonal orhexagonal shapes.
 18. The semiconductor wafer of claim 15, wherein theplurality of dice have at least one notched corner, square-notchedcorner or curve-notched corner.
 19. The semiconductor wafer of claim 15,wherein the saw streets are non-rectilinear.
 20. The semiconductor waferof claim 15, wherein the sacrificial structure has at least onedimension greater than the minimum distance between the two adjacentdice.
 21. The semiconductor wafer of claim 20, wherein a width of theplurality of saw streets is less than the at least one dimension of thesacrificial structure.
 22. A reticle for use in forming structures on asemiconductor wafer, the reticle comprising: a plurality of die imageshaving non-rectangular shapes with at least one notched corner; and aplurality of saw street images defined between the plurality of dieimages, wherein at an intersection of two of the plurality of saw streetimages, a distance is defined between corners of two adjacent die imagesthat is greater than a minimum distance between the two adjacent dieimages.
 23. The reticle of claim 22 further comprising: a sacrificialstructure image disposed at the intersection of two of the plurality ofsaw street images, wherein the sacrificial structure image has at leastone dimension greater than the minimum distance between the two adjacentdie images.
 24. A method of forming structures on a semiconductor wafer,the method comprising: forming a plurality of dice havingnon-rectangular shapes with at least one notched corner; and forming aplurality of saw streets defined between the plurality of dice, whereinat an intersection of two of the plurality of saw streets, a distance isdefined between corners of two adjacent dice that is greater than aminimum distance between the two adjacent dice.
 25. The method of claim24 further comprising: forming a sacrificial structure at theintersection of two of the plurality of saw streets, wherein thesacrificial structure has at least one dimension greater than theminimum distance between the two adjacent dice.